jonathan karl has been tracking the administration's response. jon, tell us the news. >> reporter: just a short while ago, the white house informed us that the president will travel to boston on thursday to attend an interfaith memorial service for the victims of the marathon bombing. earlier today the president summoned his national security team to the white house, including his attorney general, the secretary of homeland security and the fbi director, for a meeting in the oval office, to get the latest on the investigation. right after that meeting, diane, the president came into the white house briefing room, and he told us that the american people refuse to be terrorized. but he also made it clear that this bombing was an act of terrorism. >> this was a heinous and cowardly act, and given what we now know about what took place, the fbi is investigating it as an act of terrorism. any time bombs are used to target innocent civilians, it is an act of terror. what we don't yet know, however, is who carried out this attack, or why, whether it was